I Have two OLD P99 mags. The P99 mags are made by Mecgar, who also make Beretta 92 mags (at one time, they made the factory mags).
Anyway - these two 10 round mags no longer lock the slide back. And, they go all the way back to when Interarms imported the P99 - so S&W won't honor any warranty.
Anyway - I kinda thought that a 10 or 15 round Beretta mag spring may solve the issue. Does anyone have one? Maybe you replaced your mag springs with Wollf springs and are not using a spring or two?
I'd really appreciate it.